fix(nix): add ffmpeg libs to runtime dependencies (#422)

Author: kasimeka

.gitignore

@@ -4,3 +4,6 @@
 /out
 .DS_Store
 node_modules
+
+# nix build output path
+/result

flake.nix

@@ -79,6 +79,7 @@
           pkgs.pkg-config
           pkgs.ffmpeg_8.dev
         ];
+        buildInputs = [pkgs.ffmpeg_8.lib];
         meta.mainProgram = "neothesia-cli";
         src = workspace;
       };